So far, vinylidene fluoride (PVdF) has been proposed for the use on a film for a film capacitor because of its high dielectric constant. However, it is known that temperature dependency of dielectric loss tangent (tan δ) of PVdF is high and dielectric loss tangent rises rapidly at high temperatures (80° C. or more) (Patent Document 1, etc.). As dielectric loss tangent is increased, namely as a dielectric loss is increased, a film capacitor becomes unstable, thereby impairing reliability on a circuit.
Patent Document 1 describes that by blending polyether such as polyoxymethylene in a given amount to PVdF, a dielectric loss of PVdF can be decreased and can be decreased lower than that of PVdF itself.
However, in the case of blending polyether, there is room for improvement in high temperature dependency of dielectric loss.
In the meantime, use of a variety of characteristics obtained by mixing various other resins to PVdF has been generally carried out. For example, Patent Document 1 describes mixing of polyvinyl acetate, acrylic resin or the like to PVdF to prepare a thermoplastic resin composition for molding and coating.
In order to prepare such a composition comprising PVdF, mixing of a hydrophilic polymer such as polycellulose acetate is also known (Patent Document 2), and this composition is formed into a porous film to be used as a semipermeable film for ultrafiltration and a semipermeable film for ultrafine filtration.    Patent Document 1: JP60-199046A    Patent Document 2: JP2-78425A